This invention relates to apparatus and method for performing surgery. More particularly this invention relates to apparatus for ultrasonically removing neurological type organic tissues in a manner which limits destruction of adjacent tissue. In neurological surgery as for instance the removal of benign tumorous tissues, the present technique is to evacuate the central volume of the tumor by using an electrosurgical loop or a sharp spooned curette after which the remaining tumor shell is dissected from the healthy tissue. The problem with this procedure is the fact that cutting is performed forward of the visible tissue which makes it virtually impossible for the surgeon to see what is being cut. Therefore the cutting edge may penetrate blood vessels within the area of the tumor causing severe bleeding and further limiting visibility in the operative site. Of greater danger is the possibility of damage to a major blood vessel or a nerve such as the carotid artery or the optic nerve, either of which represents severe trauma to the patient. It would be advantageous to provide some other surgical tool for cutting and removing neurological tissue which does not present or minimize such problems.
Ultrasonically vibrated surgical instruments are known and are being employed in certain type of specialized surgery, particularly in dentistry to clean tooth surfaces, and in the removal of cataracts. For instance prior art, illustrative of the former is shown by U.S. Pat. No. 2,990,616 issued July 4, 1961 for Ultrasonic Cutting Tool, while instruments for accomplishing the latter type of surgery is illustrated by U.S. Pat. No. 3,589,363 issued June 29, 1971 to A. Banko and C. D. Kelman for a Material Removal Apparatus and Method Employing High Frequency Vibrations.
Prior art apparatus such as that disclosed by the aforesaid U.S. Pat. No. 3,589,363 for ultrasonic aspiration of tissues such as cataracts has been examined and found to be effective therefor. The apparatus according to the aforementioned Banko et al. patent employs a handpiece and has a tip which is longitudinally vibrated and designed for precise removal of small quantities of non-vascularized tissues, such as found in a cataract lens. It relies on the fact that cataract surgery takes place in a small enclosed operative site where the application of suction through the hollow center of the tip staying in a relatively stationary position. This is important in cataract surgery because of the possibility of damage to other coextensive tissue structures.
Brain, neurological and other soft tissues present a different set of conditions than those encountered in cataract surgery. Since relatively larger masses of tissue are involved here, including the requirement for speedy and precise removal of undesired tissue (with minimum trauma or damage to adjacent healthy tissue) apparatus suitable for cataract removal is generally ineffective.
Further, (senile) cataract tissue is relatively hard, brittle and (possibly) calcified in contrast to other soft tissues such as neurological (brain), liver, lung tissue, etc., for example. Apparently the more elastic and fibrous a tissue, the greater difficulty there exists in fragmenting and aspirating it according to the methods and apparatus disclosed by Banko et al.